Sir Alan Sugar will take up a job as "Enterprise Tsar' in Gordon Brown's Government, paving the way for a peerage for the British entrepreneur.
Sir Alan, a long-standing friend of the Prime Minister, today spoke out in support of Mr Brown, describing him as "resolute".
As Mr Brown's position was undermined further by more resignations from his Cabinet, the multi-millionaire businessman gave him his full backing.
Reports suggest he will be rewarded for his new role with a position in the House of Lords.
Sir Alan was seen entering Number 10 on Thursday morning but his spokesman declined to comment on any appointment.
Some business leaders welcomed his appointment, saying he was the big hitter needed to fight small companies' corner. Stephen Alambritis, at the Federation of Small Businesses, said: "We have asked the Governement for someone to mediate between banks and small businesses.
"We hope Sir Alan will fulfill this role. He started off his career as a small business owner so has done the journey. We look forward to working with him."